The four stages of fracture include: the first period, the hematoma mechanization period, which is completed within 2-3 weeks after the fracture. Because the periosteum around the fracture is damaged after the fracture, the blood vessels will rupture and form a hematoma, which will coagulate, resorb and mechanize. The second period, the period of scab formation, is 4-6 weeks after the fracture. After the fracture, the fracture end will stimulate the formation of osteoblasts, which will promote the formation of scab. The scab formed during this period is a fibrous scab, which is not visible on the X-ray. The third period, when the fracture continues to heal, is called the osseous healing period, which occurs 8-12 weeks after the fracture, and the bone scabs formed at this time are called osseous scabs, which are stronger. The fourth period is the fracture remodeling and shaping period, when the fracture bony scab is formed, the fracture remodeling and shaping will reach the normal shape of the bone before the fracture, when the fracture remodeling and shaping period is over, the fracture healing is finished and the normal bone shape is restored.